1. Field of the Invention
This invention relates to a lighting device, in particular, to a lighting device to emit a light which hardly reduces the users' recognition and judgement when used in illumination.
2. Description of the Prior Art
In case of doing visual tasks, the use of inappropriate illumination often reduces workers' or operators' recognition and judgement. For example, when a video display terminal (VDT) task is loaded under a poor illumination, the operator hardly recognizes the fine characters and details of figures on the data displaying unit and/or keyboard, thus resulting in the increase of misoperations and/or extension of operation time which reduce operation efficiency. In the case of color coordination wherein careful distinction of colors is indispensable, the use of inappropriate illumination also results in the increase of mistask and/or extension of working time which reduces woking efficiency.
Thus, in various tasks wherein working and operation efficiencies are greatly dependent on human recognitive and judgemental faculties, it is indispensable to use an illumination which keeps these faculties in high levels.
However, past discussions on illumination have been focused on its clarity and color rendering properties and no discussion has been actually made on the relationship between illumination and human recognition and/or judgement.